The disclosure of Japanese Patent Application No. HEI 11-371, 847 filed on Dec. 27, 1999, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a hybrid drive apparatus that uses a combustion engine and an electric motor as power sources and, more particularly, to connecting structures between axes in a hybrid drive apparatus.
2. Description of the Related Art
Hybrid drive apparatuses that use a combustion engine (hereinafter referred to as xe2x80x9cenginexe2x80x9d) and an electric motor (hereinafter referred to as xe2x80x9cmotorxe2x80x9d) as power sources allow various power train arrangements as power from each power source may be transmitted to a differential device in a number of ways. Among such apparatuses, a drive apparatus having a structure that is excellent in the respect of transmitting output from the engine and output from the electric motor to a differential device with an arbitrary gear ratio set is disclosed in the Japanese Patent Application Laid-Open No. HEI 8-183347. This drive apparatus comprises an engine and an electric power generator disposed on a first axis, an electric motor disposed on a second axis, a countershaft disposed on a third axis, and a differential device disposed on a fourth axis. The engine and the electric power generator are connected to a countershaft through a differential gear device. FIG. 7 depicts actual positional relationships for this apparatus. The electric motor and the differential device are directly connected to the countershaft. Therefore, the gear ratio of a pair of gears connecting the engine and the countershaft and the gear ratio of a pair of gears connecting the electric motor and the countershaft can be arbitrarily set independently of each other.
With regard to engines, it is often the case that power train requirements vary depending on vehicle orientation. For the fuel economy-oriented vehicle, the total gear ratio from the engine to wheels is usually set to a relatively high value for optimal economy. For the accelerating performance-oriented vehicle, the total gear ratio from the engine to the wheels is usually set to a relatively low value for optimal performance. To meet these vehicular requirements in the aforementioned hybrid drive apparatus, the total gear ratio from the engine to the wheels may be selected or changed by selecting or changing the diameters for each of the gears connecting the differential gear device and the countershaft, that is, by changing the diameter of a drive gear a on a first axis I and a driven gear b on a third axis III as indicated by broken lines in FIG. 7. However, in FIG. 7, such changes in the total gear ratio from the engine to the wheels require changes in the diameters of the pair of gears connecting the electric motor and the countershaft. This must be accomplished by appropriately selecting diameters for a drive gear c on a second axis II and the driven gear b on the third axis III. Thus, the electric motor to wheel gear ratio is automatically affected. This is a significant disadvantage. Furthermore, as the diameter of the drive gear a is changed to a gear axe2x80x2 shown in FIG. 7, the inter-axis distance between the countershaft on the third axis III and the differential device on a fourth axis IV changes as indicated by axis IIIxe2x80x2 in FIG. 7. Therefore, the shape of a housing surrounding this arrangement must also be changed.
Finally, as the drive gears a, c mesh with the same tooth face of the common counter driven gear b, a tooth face precision of the drive gear a with respect to the counter driven gear b and a tooth face precision of the drive gear c with respect to the driven gear b must be simultaneously achieved in order to avoid unacceptable gear noise. Therefore, a great number of man-hours must be consumed to meet the precision requirements for this apparatus.
Accordingly, a first object of the invention is to provide a hybrid drive apparatus that allows a change in the overall gear ratio between the engine and the countershaft without necessitating a change in the gear ratio between the motor and the countershaft.
A second object of the invention is to separately provide a hybrid drive apparatus that allows a change in the gear ratio between the motor and the countershaft without necessitating a change in the gear ratio between the engine and the countershaft.
A third object of the invention is to separately provide a hybrid four-axis drive apparatus that makes it possible to arbitrarily set and change an engine-side total gear ratio and, if necessary, an electric motor-side total gear ratio without necessitating a change in the positions of any of the axes.
In accordance with a first aspect of the invention, a hybrid drive apparatus includes an engine and an electric power electric power generator that are disposed on a first axis, an electric motor disposed on a second axis, a countershaft disposed on a third axis, and a differential device disposed on a fourth axis. The engine and the electric power generator are connected to the countershaft via a differential gear device, and the electric motor and the differential device are directly connected to the countershaft. The differential gear device and the countershaft are connected by a first pair of gears that mesh with each other, and the electric motor and the countershaft are connected by a second pair of gears that mesh with each other, and the countershaft and the differential device are connected by a third pair of gears that mesh with each other.
In this hybrid drive apparatus, the power transmission from the engine side to the countershaft through the first pair of gears and the power transmission from the electric motor side to the countershaft through the second pair of gears are performed in different paths with respect to the countershaft. Therefore, the output from the engine side and the output from the electric motor can be completely independent from each other, and the total gear ratios on the two sides to the differential device can be freely set. Furthermore, when the gear ratios on the two sides are selected or changed, it is unnecessary to change the inter-axis distances between the four axes. As a result, the same casing can be used before and after the gear ratio settings are changed.
In accordance with a second aspect of the invention, a hybrid drive apparatus includes an engine and an electric power generator that are disposed on a first axis, an electric motor disposed on a second axis, a countershaft disposed on a third axis, and a differential device disposed on a fourth axis. The engine and the electric power generator are connected to the countershaft through a differential gear device, and each of the electric motor and the differential device is directly connected to the countershaft. The electric motor is connected to the countershaft through a speed reducing mechanism disposed on the second axis, and the differential device is directly connected to the countershaft. The differential gear device and the countershaft are connected by a first pair of gears that mesh with each other, and the electric motor and the countershaft are connected by a second pair of gears that mesh with each other, and the countershaft and the differential device are connected by a third pair of gears that mesh with each other.
In this hybrid drive apparatus, the power transmission from the engine side to the countershaft through the first pair of gears and the power transmission from the electric motor to the countershaft through the second pair of gears are performed in different paths with respect to the countershaft. Therefore, the output from the engine side and the output from the electric motor can be completely independent from each other. Hence, the total gear ratio from the engine side to the differential device can be freely set without affecting the gear ratio from the motor to the differential device. By changing the gear ratio of the speed reducing mechanism, the gear ratio on the electric motor side can be changed without affecting the total gear ratio of the path from the engine side to the differential device. Furthermore, it is unnecessary to change the inter-axis distances between the four axes when the gear ratios on the two sides are selected or changed. As a result, the same casing can be used before and after the gear ratio settings are changed.
In accordance with a third aspect of the invention, a hybrid drive apparatus includes an engine, an electric power generator and an electric motor that are disposed on a first axis, a countershaft disposed on a third axis, and a differential device disposed on a fourth axis. The engine and the electric power generator are connected to the countershaft through a differential gear device, and the electric motor and the differential device are directly connected to the countershaft. The differential gear device and the countershaft are connected by a first pair of gears that mesh with each other, and the electric motor and the countershaft are connected by a second pair of gears that mesh with each other, and the countershaft and the differential device are connected by a third pair of gears that mesh with each other.
In this hybrid drive apparatus, the power transmission from the engine side to the countershaft by the first pair of gears and the power transmission from the electric motor side to the countershaft by the second pair of gears are performed in different paths with respect to the countershaft. Therefore, the output from the engine side and the output from the electric motor can be completely independent from each other, and the total gear ratios from the engine and motor to the differential device can be freely and independently set. Furthermore, when the gear ratios on the two sides are selected or changed, it is unnecessary to change the inter-axis distances between the three axes. As a result, the same housing may be used before and after the gear ratio settings are changed.
In the hybrid drive apparatus of the first and second aspects of the invention, each of the first, second and third pairs of gears may be formed by two gears disposed at different positions along an axis of the countershaft. In this aspect of the invention, each of the gears meshes with only one other gear. Therefore, the structure is advantageous in reducing the gear noise, and the man-hours for processing the gears can be reduced.
Furthermore, in the invention, the second and third pairs of gears may be formed by three gears consisting of a common gear on the countershaft, and an electric motor-side gear and a differential device-side gear that mesh with the common gear at different positions in a direction of an axis.
In this structure, a gear connecting the electric motor and the countershaft and a gear connecting the countershaft and the differential device are one and the same gear. However, due to the mesh positions shifted from each other in the direction of the axis, the common gear can have different tooth faces. Therefore, this structure, too, is advantageous in reducing the gear noise, and the man-hours for processing the gears can be reduced.